[PATCH] Fix to virtual terminal UTF-8 mode handling

[PATCH] Fix to virtual terminal UTF-8 mode handling

[Paul LeoNerd Evans]

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This patch fixes a bug in the virtual terminal driver, whereby the UTF-8
mode is reset to "off" following a console reset, such as might be
delivered by mingetty, screen, vim, etc...

Rather than resetting to hardcoded "0", it gets reset on or off, as
determined by a new sysctl located in /proc/tty/vt/default_utf8_mode.
This patch is best accompanied with an addition of the following line to
the system's init scripts:

  echo 1 >/proc/tty/vt/default_utf8_mode

Following this, all resets to the console will leave it with UTF-8 mode
on.

The default behaviour of this sysctl is as before, without the patch.
Namely, UTF-8 mode is switched off on reset. [I.e applying this patch
does not affect default behaviour].


Signed-off-by: Paul Evans <leonerd@leonerd.org.uk>


--- linux-2.6.11/drivers/char/vt.c	2005-05-04 02:01:08.000000000
+0100 +++ linux-2.6.11-utfswitch/drivers/char/vt.c	2005-05-07
22:41:58.000000000 +0100 @@ -93,6 +93,7 @@
 #include <linux/pm.h>
 #include <linux/font.h>
 #include <linux/bitops.h>
+#include <linux/proc_fs.h>
 
 #include <asm/io.h>
 #include <asm/system.h>
@@ -162,6 +163,15 @@
 static int blankinterval = 10*60*HZ;
 static int vesa_off_interval;
 
+/*
+ * When resetting a console, do we start in UTF-8 mode or not?
+ * 0 = no, 1 = yes
+ */
+static int default_utf8_mode = 0;
+
+struct proc_dir_entry *proc_vt_dir;
+struct proc_dir_entry *proc_default_utf8_mode;
+
 static DECLARE_WORK(console_work, console_callback, NULL);
 
 /*
@@ -1472,7 +1482,7 @@
 	charset		= 0;
 	need_wrap	= 0;
 	report_mouse	= 0;
-	utf             = 0;
+	utf             = default_utf8_mode;
 	utf_count       = 0;
 
 	disp_ctrl	= 0;
@@ -2530,6 +2540,63 @@
 	reset_terminal(currcons, do_clear);
 }
 
+static int proc_write_default_utf8_mode(struct file *file, const char
*buffer,
+			unsigned long count, void *data)
+{
+	char temp[16];
+	int len;
+
+	if (count > sizeof(temp)-1)
+		len = sizeof(temp)-1;
+	else
+		len = count;
+
+	if (copy_from_user(temp, buffer, len))
+		return -EFAULT;
+
+	temp[len] = 0;
+
+	/* No effect if empty or >1 character long */
+	if (temp[0] == 0 || (temp[1] != '\n' && temp[1] != 0)) {
+		return len;
+	}
+
+	/* No effect if outside the range 0<=x<=1 */
+	if (temp[0] < '0' || temp[0] > '1') {
+		return len;
+	}
+
+	default_utf8_mode = (temp[0] - '0');
+
+	return len;
+}
+
+static int proc_read_default_utf8_mode(char *page, char **start, off_t
off,
+			int count, int *eof, void *data)
+{
+	return sprintf(page, "default_utf8_mode = %d\n",
default_utf8_mode); +}
+
+static int init_proc(void)
+{
+	proc_vt_dir = proc_mkdir("tty/vt", NULL);
+
+	if (!proc_vt_dir)
+		return -ENOMEM;
+
+	proc_default_utf8_mode = create_proc_entry("default_utf8_mode",
0644, proc_vt_dir); +
+	if (!proc_default_utf8_mode)
+		return -ENOMEM;
+
+	proc_default_utf8_mode->owner = THIS_MODULE;
+	proc_default_utf8_mode->data = &default_utf8_mode;
+	proc_default_utf8_mode->write_proc =
proc_write_default_utf8_mode;
+	proc_default_utf8_mode->read_proc = proc_read_default_utf8_mode;
+
+	return 0;
+}
+
 /*
  * This routine initializes console interrupts, and does nothing
  * else. If you want the screen to clear, call tty_write with
@@ -2612,6 +2679,8 @@
 
 int __init vty_init(void)
 {
+	int ret;
+
 	vcs_init();
 
 	console_driver = alloc_tty_driver(MAX_NR_CONSOLES);
@@ -2638,6 +2707,11 @@
 #ifdef CONFIG_MDA_CONSOLE
 	mda_console_init();
 #endif
+
+	ret = init_proc();
+	if (ret)
+		return ret;
+
 	return 0;
 }
 


-- 
Paul "LeoNerd" Evans

leonerd@leonerd.org.uk
ICQ# 4135350       |  Registered Linux# 179460
http://www.leonerd.org.uk/

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Re: [PATCH] Fix to virtual terminal UTF-8 mode handling

[Paul LeoNerd Evans]

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Apologies, my mail client annoyingly wrapped the patch; here it is
fixed.


diff -urN --exclude-from=diff-exclude linux-2.6.11/drivers/char/vt.c linux-2.6.11-utfswitch/drivers/char/vt.c
--- linux-2.6.11/drivers/char/vt.c	2005-05-04 02:01:08.000000000 +0100
+++ linux-2.6.11-utfswitch/drivers/char/vt.c	2005-05-07 22:41:58.000000000 +0100
@@ -93,6 +93,7 @@
 #include <linux/pm.h>
 #include <linux/font.h>
 #include <linux/bitops.h>
+#include <linux/proc_fs.h>
 
 #include <asm/io.h>
 #include <asm/system.h>
@@ -162,6 +163,15 @@
 static int blankinterval = 10*60*HZ;
 static int vesa_off_interval;
 
+/*
+ * When resetting a console, do we start in UTF-8 mode or not?
+ * 0 = no, 1 = yes
+ */
+static int default_utf8_mode = 0;
+
+struct proc_dir_entry *proc_vt_dir;
+struct proc_dir_entry *proc_default_utf8_mode;
+
 static DECLARE_WORK(console_work, console_callback, NULL);
 
 /*
@@ -1472,7 +1482,7 @@
 	charset		= 0;
 	need_wrap	= 0;
 	report_mouse	= 0;
-	utf             = 0;
+	utf             = default_utf8_mode;
 	utf_count       = 0;
 
 	disp_ctrl	= 0;
@@ -2530,6 +2540,63 @@
 	reset_terminal(currcons, do_clear);
 }
 
+static int proc_write_default_utf8_mode(struct file *file, const char *buffer,
+			unsigned long count, void *data)
+{
+	char temp[16];
+	int len;
+
+	if (count > sizeof(temp)-1)
+		len = sizeof(temp)-1;
+	else
+		len = count;
+
+	if (copy_from_user(temp, buffer, len))
+		return -EFAULT;
+
+	temp[len] = 0;
+
+	/* No effect if empty or >1 character long */
+	if (temp[0] == 0 || (temp[1] != '\n' && temp[1] != 0)) {
+		return len;
+	}
+
+	/* No effect if outside the range 0<=x<=1 */
+	if (temp[0] < '0' || temp[0] > '1') {
+		return len;
+	}
+
+	default_utf8_mode = (temp[0] - '0');
+
+	return len;
+}
+
+static int proc_read_default_utf8_mode(char *page, char **start, off_t off,
+			int count, int *eof, void *data)
+{
+	return sprintf(page, "default_utf8_mode = %d\n", default_utf8_mode);
+}
+
+static int init_proc(void)
+{
+	proc_vt_dir = proc_mkdir("tty/vt", NULL);
+
+	if (!proc_vt_dir)
+		return -ENOMEM;
+
+	proc_default_utf8_mode = create_proc_entry("default_utf8_mode", 0644, proc_vt_dir);
+
+	if (!proc_default_utf8_mode)
+		return -ENOMEM;
+
+	proc_default_utf8_mode->owner = THIS_MODULE;
+	proc_default_utf8_mode->data = &default_utf8_mode;
+	proc_default_utf8_mode->write_proc = proc_write_default_utf8_mode;
+	proc_default_utf8_mode->read_proc = proc_read_default_utf8_mode;
+
+	return 0;
+}
+
 /*
  * This routine initializes console interrupts, and does nothing
  * else. If you want the screen to clear, call tty_write with
@@ -2612,6 +2679,8 @@
 
 int __init vty_init(void)
 {
+	int ret;
+
 	vcs_init();
 
 	console_driver = alloc_tty_driver(MAX_NR_CONSOLES);
@@ -2638,6 +2707,11 @@
 #ifdef CONFIG_MDA_CONSOLE
 	mda_console_init();
 #endif
+
+	ret = init_proc();
+	if (ret)
+		return ret;
+
 	return 0;
 }
 



-- 
Paul "LeoNerd" Evans

leonerd@leonerd.org.uk
ICQ# 4135350       |  Registered Linux# 179460
http://www.leonerd.org.uk/

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Re: [PATCH] Fix to virtual terminal UTF-8 mode handling

[Andrew Morton]

Paul LeoNerd Evans <leonerd@leonerd.org.uk> wrote:
>
>  This patch fixes a bug in the virtual terminal driver, whereby the UTF-8
>  mode is reset to "off" following a console reset, such as might be
>  delivered by mingetty, screen, vim, etc...

Is it a bug?  What did earlier kernels do?  2.4.x?

>  Rather than resetting to hardcoded "0", it gets reset on or off, as
>  determined by a new sysctl located in /proc/tty/vt/default_utf8_mode.
>  This patch is best accompanied with an addition of the following line to
>  the system's init scripts:
> 
>    echo 1 >/proc/tty/vt/default_utf8_mode
> 
>  Following this, all resets to the console will leave it with UTF-8 mode
>  on.
> 
>  The default behaviour of this sysctl is as before, without the patch.
>  Namely, UTF-8 mode is switched off on reset. [I.e applying this patch
>  does not affect default behaviour].

Presumably userspace knows what mode the user wants the terminal to be
using.  Shouldn't userspace be resetting that mode after a reset?

Re: [PATCH] Fix to virtual terminal UTF-8 mode handling

[Daniel Jacobowitz]

On Tue, May 17, 2005 at 07:58:48PM -0700, Andrew Morton wrote:
> Paul LeoNerd Evans <leonerd@leonerd.org.uk> wrote:
> >
> >  This patch fixes a bug in the virtual terminal driver, whereby the UTF-8
> >  mode is reset to "off" following a console reset, such as might be
> >  delivered by mingetty, screen, vim, etc...
> 
> Is it a bug?  What did earlier kernels do?  2.4.x?

I'd be inclined to think that this is more of a terminfo issue.  If you
want your terminal to reset into UTF-8, use a terminfo entry with the
appropriate command string instead of the current one - this would be
the 'rs1' capability:

  rs1=\Ec\E]R

That's reset console to default, reset palette.

> Presumably userspace knows what mode the user wants the terminal to be
> using.  Shouldn't userspace be resetting that mode after a reset?

There's no standard way to represent this in userspace.  But yeah.

-- 
Daniel Jacobowitz
CodeSourcery, LLC

Re: [PATCH] Fix to virtual terminal UTF-8 mode handling

[Paul LeoNerd Evans]

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On Tue, 17 May 2005 19:58:48 -0700
Andrew Morton <akpm@osdl.org> wrote:

> Paul LeoNerd Evans <leonerd@leonerd.org.uk> wrote:
> >
> >  This patch fixes a bug in the virtual terminal driver, whereby the
> > UTF-8 mode is reset to "off" following a console reset, such as might
> > be delivered by mingetty, screen, vim, etc...
> 
> Is it a bug?  What did earlier kernels do?  2.4.x?

I haven't checked earlier 2.4 kernels, but I know the 2.6 ones have done
this for quite some time; a good year or so at least.

> Presumably userspace knows what mode the user wants the terminal to be
> using.  Shouldn't userspace be resetting that mode after a reset?

Well, that does require changes to a lot of the programs that talk to the
console, moreover, they now need to be sensitive to whether it is in
UTF-8 mode, where previously they did not. E.g. consider mingetty...

Also, as I understand it, there is one keyboard map, and one console font
for the entire virtual console system - either they are UTF-8, or not. It
doesn't really make sense to be switching these about.

Moreover, this code also affects dynamic creation of new virtual
consoles. E.g. when debian's "oh no, I can't start the X server" ncurses
dialog appears, without my patch it prints UTF-8 characters on a new
console, tty8, on a console that isn't set to display them, and mass
breakage results. Now, it all happens cleanly, because the new console is
already in UTF-8 mode.

Were this to be pushed to userland, every program that outputs data would
need to detect the UTF-8 mode of the console, and set it appropriately.
Moreover, they would need to perform this logic only on a Linux virtual
console; such things as XTerm or Gnome-terminal do it automatically.

-- 
Paul "LeoNerd" Evans

leonerd@leonerd.org.uk
ICQ# 4135350       |  Registered Linux# 179460
http://www.leonerd.org.uk/

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Re: [PATCH] Fix to virtual terminal UTF-8 mode handling

[Paul LeoNerd Evans]

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On Tue, 17 May 2005 23:10:30 -0400
Daniel Jacobowitz <dan@debian.org> wrote:

> I'd be inclined to think that this is more of a terminfo issue.  If you
> want your terminal to reset into UTF-8, use a terminfo entry with the
> appropriate command string instead of the current one - this would be
> the 'rs1' capability:
> 
>   rs1=\Ec\E]R
> 
> That's reset console to default, reset palette.

Unfortunately, that doesn't work. Doing it that way means that any
program running on a host whose terminfo is so configured, would force
UTF-8 mode on, when it issues a reset to a Linux console, regardless of
which machine that is on (e.g. telnet, ssh,...). Furthermore, it would do
so regardless of whether we want UTF-8 mode, or not. Again with my patch
it is a user configurable matter whether they want UTF-8 or not. This
terminfo entry forces it to happen.

That said, I am planning a whole bunch of other changes to terminfo; my
repeated wrestling with xterm recently on the regard of modified cursor
keys (e.g. Ctrl+left) has lead me to conclude the whole system needs a
bit of an overhaul... But that's somewhat off-topic to the kernel.. :)

-- 
Paul "LeoNerd" Evans

leonerd@leonerd.org.uk
ICQ# 4135350       |  Registered Linux# 179460
http://www.leonerd.org.uk/

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